The invention relates to a valve for a fuel tank of a motor vehicle which has a float valve and a connection to atmosphere. The invention also relates to a motor vehicle fuel tank equipped with such a valve.
Vent valves for integrated expansion volumes of fuel tanks are known which limit the maximal level in the fuel tank and thus create an integrated compensation volume. These may be float valves for the refueling venting which can also be combined with rollover valves. At a maximal level in the fuel tank, the existing number of float valves are closed, so that no venting takes place in this condition.
The known floater valves may be provided with a by-pass bore so that, in the event of a volume expansion of the fuel as a result of a temperature rise in the fuel tank, a pressure compensation can take place. This has the disadvantage that, as a result of a slow topping-off during the refueling operation, the fuel compensation volume may be filled.
When the floater valves are combined with rollover valves, it is disadvantageous that, when several such valves are arranged, the leakages of the individual rollover valves will add up in the event of a rollover.
It is an object of the invention to provide a valve which permits a compact construction. It is also an object of the invention to provide a fuel tank of a motor vehicle having at least one such valve so that the fuel tank has a simplified construction.
The object indicated for the valve is achieved by a valve of the above noted type; wherein a pressure control valve is arranged on the valve, which pressure control valve opens up at a defined excess pressure in the fuel tank, wherein a refueling venting opening is constructed in the valve, wherein the refueling venting opening can be closed by a sealing plate, wherein the sealing plate has an operational venting opening, wherein the operational venting opening can be closed by a c displaceable closing part, and wherein the displacement of the closing part takes place as a function of the position of a float arranged on a float lever.
The object indicated for the fuel tank is achieved by utilizing at least one of these valves in a compensation volume integrated in a fuel tank having at least one chamber, wherein each valve comprises a venting valve chamber having a refueling venting opening, a sealing plate disposed to selectively open and close the refueling venting opening, an operational venting opening in the sealing plate, a displaceable closing part disposed to selectively open and close the operational venting opening, and a fuel level responsive float assembly operable to control the displaceable closing part as a function of fuel level in the fuel tank.
In the case of the valve according to the invention, a pressure valve and a valve operating in two stages, which is controlled by way of a float, are advantageously integrated in a single component. In the following, the valve controlled by way of the float will be called a float valve. In the case of the float valve, the refueling venting takes place in one stage and the venting in the driving operation takes place in the other stage. By means of the float valve, the fuel level in the fuel tank can advantageously be limited by way of the refueling venting. In addition, it is advantageous that a venting of the fuel tank can take place in the driving operation as well as during a side tilt of the fuel tank or of the motor vehicle.
Another advantage of the valve according to the invention consists of the fact that, when a float valve is completely closed, a pressure compensation can take place by way of the integrated pressure valve. Finally, after a complete closing of the float valve, the valve according to the invention prevents a filling of the compensation volume by a slow topping-off.
The integration of three functions in one housing results in a compact construction. The combination of several functions in one component also has the advantage that the costs of the parts and the expenditures for the preassembly and assembly are reduced.
It is also advantageous that, by means of the valve according to the invention, a variable limitation of the filling level in the fuel tank can be achieved solely by a change of the length and/or of the shape of a float lever arm to which the float is fastened. Advantageously, by adjusting the length of the float lever arm to which the float is fastened, the contact pressure force of the existing valves on their respective sealing seat as well as the opening force of the valves from the sealing seat can also be defined.
In the case of a fuel tank equipped with the valve according to the invention, a penetration of fuel into a vent line situated in the fuel tank is prevented in the event of sloshing movements of the fuel during the driving operation. As a result of the wave motion of the fuel sloshing in the fuel tank, the valve is already closed by way of the float before the fuel surge reaches the valve seat.